6.2 Emulsions
Oils do not dissolve in water. If oil and water are shaken together tiny droplets of one liquid suspend in the other liquid. This is called an emulsion. You can get an oil-in-water emulsion whereby oil droplets are suspended in water; examples include ice cream, salad cream and milk. Or you can have a water-in-oil emulsion whereby water droplets are suspended in oil; examples include margarines, skin cream and moisturising lotion.
Emulsions are more viscous than the oil or water that they contain. Emulsions are used because they give a substance a better appearance, texture and coating ability. For example, salad dressing is made from olive oil and vinegar. Salad dressing covers salad better than covering salad in either olive oil or vinegar.
The more oil that you put into an emulsion, the thicker the emulsion will become. For example, full fat milk is very runny because it only contains about 3% oil and the rest is water. Single cream is thicker than milk and it contains about 18% oil. Double cream is thicker than both single cream and milk and it contains about 50% oil.
Emulsions are more viscous than the oil or water that they contain. Emulsions are used because they give a substance a better appearance, texture and coating ability. For example, salad dressing is made from olive oil and vinegar. Salad dressing covers salad better than covering salad in either olive oil or vinegar.
The more oil that you put into an emulsion, the thicker the emulsion will become. For example, full fat milk is very runny because it only contains about 3% oil and the rest is water. Single cream is thicker than milk and it contains about 18% oil. Double cream is thicker than both single cream and milk and it contains about 50% oil.
Emulsifiers (HT Only)
If emulsions are left to stand, the oil and water will separate out. Emulsifiers prevent oil and water from separating because emulsifiers are molecules with one part that is attracted to water and another part that is attracted to oil. The part that is ‘water loving’ is called the hydrophilic end. The bit that is ‘water hating’ (i.e. oil loving) is called the hydrophobic end.
The oil droplets are surrounded by emulsifiers with the hydrophilic head dissolved in the water and the hydrophobic tails dissolved into the oil. Other oil droplets are repelled by the hydrophilic head meaning that the oil droplets do not join together.
An egg yolk contains a natural emulsifier. Emulsifiers prevent emulsions from separating and allow products to have a longer shelf life. Also, they allow food companies to created products that contain less fat but at the same time have the texture of emulsion with more fat. However, some individuals are allergic to emulsifiers.
If emulsions are left to stand, the oil and water will separate out. Emulsifiers prevent oil and water from separating because emulsifiers are molecules with one part that is attracted to water and another part that is attracted to oil. The part that is ‘water loving’ is called the hydrophilic end. The bit that is ‘water hating’ (i.e. oil loving) is called the hydrophobic end.
The oil droplets are surrounded by emulsifiers with the hydrophilic head dissolved in the water and the hydrophobic tails dissolved into the oil. Other oil droplets are repelled by the hydrophilic head meaning that the oil droplets do not join together.
An egg yolk contains a natural emulsifier. Emulsifiers prevent emulsions from separating and allow products to have a longer shelf life. Also, they allow food companies to created products that contain less fat but at the same time have the texture of emulsion with more fat. However, some individuals are allergic to emulsifiers.